, 1887-07-08
THE GREAT AMERICAN LAKES.
Where DO They Get Their Supply of
Water 2-Change OF Lowell.

Where DO They Get Their Supply of
Water ~?-Change OF Lowell.
1t has long been known that the great
lake are subject to remarkable and SEEM
ingly capricious changes of level. These
changes are roughly registered in the va
rying volume of the st. Lawrence-that
remarkable river, itself the outlet of these
great lakes and in a sense a continuation
and part of the lakes themselves. In
some years the st. Lawrence, which
drains q watershed of over 500, 900
square miles, is much fuller all summer
than in other years. 1t leaves Lake Erie
already a broad river, forty feet deep.
At the great cataract of Niagara it de
scends with its enormous mass of nearly
400, 900 cubic feet of water in every Sec
ond of time.
This almost incomprehensible mass of
water. the drainage or overflow of all the
great lakes, varies in volume with the
level of the lakes of which it is a part.
A Milwaukee paper gives some interest
ing facts relating to these mysterious
irregular tidal movements, or change of
level, in Lake Michigan. This, the
second in size and depth of these great
laies-the largest bodies of fresh water
on the GLOBES subject to strange fluctu-
atoms, being several feet lower in some
years than in others. Lake Michigan is
n deep lake-about n thousand feet deep,
or practically as deep as Lake Superior.
1t has been, it seems, for nearly thirty
years the practice of the government to
take daily measurements of the height of
the water at Milwaukee. The water
which at that point las the ~clinging
memory of n plunge into it at the close
of July, 1S40, still %attests) is almost as
icy cold as it is at Mackinaw-is usually
a foot or two higher in summer thar it is
in winter; but in some years the varia-
ton is equal to three or four feet. This
represents, on so great n body of water,
an enormous difference. Lake Superior
alone is almost as large as the great state
of Ohio, while Lake Michigan, the direct
receiver Of its overflow, is about as large
as Massachusetts, Vermont and New
Hampshire put together. A change of
three or four feet in the level Of these
great lakes implies n difference in the
amount of water too great to be fully
understood and appreciated. The other
lakes necessarily participate in these
fluctuations; but these appear to be most
marked in Lake Michigan.
Their caus is not yet wholly under
stood. Various theories have been ad-
yanced to account for them-even to the
absurd extent of connecting them with
the ocean tidal movements. But a far
simpler explanation seems more probable.
1t would seem that the higher level in
Lake Michigan in summer and autumn
may be caused by the spring and summer
rains and the late melting snow of the
vast Canadian watershed which feeds
Lake Superior with its rushing streams
and copious rivers. In that immense lake
a rise of a single foot is equivalent to a
much greater rise in the lesser lakes of
the great system. That the fluctuations
should be irregular, showing a far greater
level in some years than in others, might
well be due to the varying quantities of
May and June rain in different years,
and to the greater quantities of snow re-
naming in those hyperborean ATTITUDES,
to be only transformed, in May and June,
into water. OF course the influx received
by the larger lake would be far less in
winter-and hence the lakes would be
lowest in winter and highest in summer
and autumn. Whatever the cause may
be, the occurrence itself of these large
fluctuations in the levels of such vast
bodies of water is one of the striking facts
in the worlds greatest fresh water sys,
tenn, and well worthy of philosophical
examination. That lake and river sys-
tenor perhaps it might be called all
one great river, 1000 miles long-is the
most interesting one on the globe. Its
greatest eNpansion-the vast Lake Su.
perior-is at a level of over 900 feet above
the level of the sea; a lake whose area is
81, 500 square miles, and whose depth is
1000 feet. The river flows on its lordly
course through the rocks of the Lauren.
tan system, the oldest on the globe, and
it receives as its affluent the dark, wild
waters of the Sagueney.-Hartford Times.